Population Biology Flashcards
The extinction process can be broken down into which 2 paradigms ?
Declining population paradigm & Small population paradigm
Describe the declining population paradigm
- Habitat destrution
- habiotat degradation
- Habitat fragmentation
- Over-hunting & live capture
Pollution - Invasive species
- Major dx outbreaks
Describe the small population paradigm
“the effets of smallness”
-> factors causing extinction under this:
- Environmental stochasticity
- Catastrophes
- Demographic stochasticity
- Genetic deterioration
Define environmental stochasticity:
random unpredictable variation in environmental factors such as temp and rainfall
Define demogrpahic stochasticity
Random unpredictable variation in sex ratios, and births ad death rates
Define Catastrophes:
extreme environemental events such as disease epidemics ro hurricanes
Define Genetic stochasticity
Inbreeding depression, loss of genetic diversity and the accumulation of deleterious mutations
What does stable age distribution demographic look like
an age pyramid with more births and young animals than old
Demographic stochasticity will reflect events due to chance alone aka:
- Births, Deaths, sexr ratio at birth
Does demographic stochasticity have a larger impact on larger or smaller populations?
smaller
Define genetic diversity
The variety of alleles & gnotypes present in the group under study
How is genetic diversity observed?
- Polymorphism
- Allelic diversity
- Average heterozygosity (expected & observed)
Allelic diversity & heterozygosity what is it?
- Different forms of an allele for a particule trait (A,b, c, d which become Ab, Bc, Cd and this is heterozygosity)
What is Expected heterozygosity also known as?
Gene Diversity
What is expected heterozygosity?
Proportion of animals int he population expected to be heterozygous if random breeding takes place
T/ F The ability of a population to evolve depends on allelic heterozygosity and the rate at which it does depends on expected heterozygosity
True
IF a population had Hardy-Weinberg equilibrium what heterozygosity would we have?
The Mean heterozygosity
What are the greatest determinants of genetic change in small vs large populations?
Large -> natural selection
Small -> chance
What is the most important factor when looking at impat of genetic drift?
Effective population size Ne
Wha is the effective population ?
The breeding population with viable offspring / portion that passes its genes into next generation
Ne definition
Number of individuals that would result in the same loss of genetic diversituy, inbreeding or genetic drift if they behaved int he manner of an iealized population
What is an idealized population?
A conceptual mating population with equal numbers of hermaphrodite individuals breeding in each generation, and Poisson variation in family sizes
What are the assumptions in an idealized population?
- No fluctuations in population size from generation to generation
- Discere (non-overlapping) generations
- Hermaphrdite individuals
- Random mating
What is Ne>50 mean?
short term - to avoid the immediate deleterious effects of inbreeding
What is Ne>500?
Long term - to allow new mutations to restore heterozygosity and additive genetic variation as rapidlu as it is lost by genetic drift
What is currently thought to be the value of Ne minimul?
Ne = 1000 or even 50000 to avoid loss fo diversity through drift
What are the ffects of genetic drift ?
- Alleles are lost (both adaptive, & maladaptive)
- Drift causes loss of genetic diversity & fixation of alleles within populations
What is Loss of diversity inversely proportional to?
Ne
The effects of Sampling in every generation are ….
cumulative
When do population bottlenecks happen?
When populations unergo susbstantial contraction
- Catastrophes
- Hbpitat loss
- Population fragmentation
When individuals in wild migrate to form new populations
When individuals from the wild are caught to form captive populations
When wild - to -wild translcoations take place
When reintroductions take place
TRUE OR FALSE. - Populations that have gone through bottlenecks have lower genetic diversity than those that have not
TRUE
What is the effect of management interventions?
Can cause bottlenecks
What does Inbreeding cause ?
- Inc in homozygozity & dec in heterozygosity
- Inc in chance of expression of recessive deleterious alleles in phenotype
How do we measure inbreeding?
Inbreeding coefficient (F) which is the probability that two alleles are identical by descent
describe effects of inbreeding depression?
- Inc juvenile mortality
- Reduced longevity
- Reduced reproduction
- Inc susceptibility to disease
T/F inbreeding increases the risk of extinction
Inbreeding inc the risk of extinction - True
Give 3 examples fo species that have experienced populations decline & extinction as a result of inbreeding
Bighorn sheep
Florida panthers
Adders
What effects of outbreeding depression caused by crosses between different sub-species or species?
Offspring maladapted to both environments
Can inbreeding and outbreeding depression occur simultaneously?
Yes (ex: Arabian oryx)
What is heterosis ?
(hybrid vigor) - improved fitness of hybrids
describe the extinction vortex
- The adverse interaction between human
impacts, inbreeding & demographic
fluctuation that results in a feedback loop
that spirals towards extinction
